1. Field of the Invention
The present invention relates to device control methods and device control apparatuses for connecting a device conforming to the universal serial bus (USB) standard to a computer, and more particularly, to a device control method and a device control apparatus which simplify a procedure required for connection to the device.
2. Description of the Related Art
A new standard for personal computers, called a universal serial bus (USB), has been recently formed and units conforming to this standard have been made commercially available. In this new standard, each of various types of peripheral units (hereinafter called devices), such as a keyboard, a mouse, and a game controller, has a connector with the same shape, and is connected to a USB port of a computer by the use of this connector.
The USB port has four pins in its inside and the pins are used for D+ and D- data lines, a power line, and the ground. Either the D+ pin or the D- pin is used to indicate that the device is connected or not connected. Whichever pin is used is pulled up (switched on) to indicate that a device is being connected, or the pin is pulled down (switched off) to indicate that a device is not connected.
Usually, one computer is provided with two USB ports of the same type. If three or more devices conforming to the USB standard are to be connected, then one or more ports may be lacking.
To handle such a case, a unit called a USB hub 9 shown in FIG. 3 has been developed, which is provided with a plurality of ports 2b having the same shape as a USB port 2a formed in a personal computer. When the USB hub 9 is connected to the USB port 2a of the personal computer, a plurality of devices can be connected to the USB port 2a of the personal computer.
The USB hub 9 shown in FIG. 3 is connected to the personal computer (PC) 2 by the use of a USB interface cable 6. A device 1, a device 2, and a device X are connected to USB ports 2b formed in the USB hub 9 with USB interface cables 7.
However, device connection with the use of a usual USB port or device connection with the use of the USB hub 9, described above, has the following inconveniences.
When a new device (device X in this case) is added to the PC 2 after devices (device 1 and device 2 in this case) have already been connected, the PC 2 does not identify the new device X and a driver for the device X does not run unless a USB connector formed at a end of the interface cable 6 is disconnected from the USB port 2a of the PC 2 then and connected again. When a connected device is removed, a device driver for the device cannot be deleted without disconnecting the USB connector and connecting it again in the same way as above.
If a USB port is formed at the back of a personal computer, it is very troublesome to disconnect a USB connector and connect it again at the back of the personal computer.
As described above, when a device is added or is removed, the D+ pin (or the D- pin) of the USB port, which has been pulled up, is pulled down and then pulled up again to send the information of each device being connected at the time before the pin is pulled down, to the personal computer through data lines 6a and 6b. In this way, the personal computer can reidentify device connections.
Without disconnecting the USB connector and connecting it again, device connections can be identified again by resetting the personal computer. In this case, it takes a long time to make the personal computer ready and the operation therefor is troublesome. In addition, if the personal computer is reset, any application programs being currently used have to be ended.
The USB hub 9 described above just allows an increase in the number of devices to be connected. When a device is added or removed, the USB connector needs to be disconnected and connected again at the USB port 2a, or the personal computer has to be reset, in the same way as in a case in which the USB hub 9 is not used.
A wireless device is easier to handle because it does not have a cable. Even for such a device, a connector needs to be disconnected and connected again, or an operation corresponding thereto is required to identify device connection again. A further operability improvement cannot be expected, which uses the advantages of a wireless device.